This is the letterhead of His All Holiness the Oecumenical Patriarch, and I recognise his signature in the margin (I have received letters from him myself).The beginning of the top Caligraphy is his name, you can make out the letters: "+ Β α ρ θ ο λ ο μ α ι ο ς " ("+Bartholomaios").

α o λ α ι ο+ Β ρ ο θ μ

The base of the Cross is the base of the ΒThe α is at the top of the ΒThe tail of the α joins the curve of the ρThe tail of the ρ joins the θ below it .....etc

I've never been able to work out the rest of it, but it contains the word "Κωνσταντινουπόλεως" ("Of Constantinople") so I assume its his full title:

+ Βαρθολομαίος ελέω Θεού Αρχιεπίσκοπος Κωνσταντινουπόλεως, Νέας Ρώμης και Οικουμενικός Πατριάρχης+ Bartholomew by the mercy of God Archbishop of Constantinople, New Rome and Oecumenical PatriarchSometimes "διάπυρος προς Θεόν ευχέτης" is added: fervent supplicant before GodThis style of signature was very common in the Byzantine culture known as "συμπίλημα" (sympilema, cypher)